OBJECT = DATA_SET_MAP_PROJECT_CATALOG DATA_SET_ID = 'MGN-V-RDRS-5-MIDR-C1-V1.0' OBJECT = DS_MAP_PROJECT_INFO_CATALOG MAP_PROJECTION_TYPE = 'SINUSOIDAL' MAP_PROJECTION_DESC = "C1-MIDRs are presented in a sinusoidal equal-area map projection. In this projection, parallels of latitude are straight lines, with constant distances between equal latitude intervals. Lines of constant longitude on either side of the projection meridian are curved since longitude intervals decrease with the cosine of latitude to account for their convergence toward the poles. This projection offers a number of advantages for storing and managing global digital data; in particular, it is computationally simple, and data are stored in a compact form. The sinusoidal equal-area projection is characterized by a projection longitude, which is the center meridian of the projection, and a scale, which is given in units of pixels/degree. The center latitude for all C1-MIDRs is the equator. A C1-MIDR is divided into an array of 56 framelets, each of which is 1024 lines by 1024 samples. Each framelet is projected with the same projection longitude and scale so that the entire C1-MIDR can be reconstructed by simply concatenating the framelets. The transformation from latitude and longitude to line and sample is given by the following equations. line = SPECLINE - lat*SCALE + 1 sample = PROJSAMP + (lon - PROJ_LON)*SCALE*cos(lat) + 0.5 SCALE = (2*PI*6051000)/(PIXSIZ*360) Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given spot on the surface. The other parameters in these equations are the names of keywords in the VICAR2 labels associated with each image. These parameters can also be found in the PDS labels of each image, but with different names. The values of parameters in the VICAR2 and PDS labels correspond to a given framelet. Thus, the computed line and sample relate to the framelet. The same equations, however, can be used for determining line and sample within a reconstructed C1-MIDR by using the values of the above parameters in the label of the first framelet, which is the one in the upper left corner of the C1-MIDR. The definitions of the VICAR2 keywords are given below. The equivalent PDS keyword name is shown in parentheses. SPECLINE (X_AXIS_PROJECTION_OFFSET) is the line number minus one on which the map projection origin occurs. The map projection origin is the intersection of the equator and the projection longitude. The value of SPECLINE is positive for images starting north of the equator and is negative for images starting south of the equator. PROJSAMP (Y_AXIS_PROJECTION_OFFSET) is the nearest sample number to the left (west) of the projection longitude. The value of PROJSAMP is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude. PROJ_LON (CENTER_LONGITUDE) is the value of the projection longitude, which is the longitude that passes through the center of the projection. PIXSIZ (MAP_SCALE) is the pixel spacing on the planet. The value in the VICAR2 label is in units of meters/pixel. PIXSIZ is 225 meters/pixel for all C1-MIDRs. There are several additional parameters in the VICAR2 and PDS labels that relate to the map projections. Those parameters that relate to sinusoidal projections or the framelet numbering are discussed below. Definitions for the remaining parameters can be found in the MIDR Software Interface Specification document or the PDS Data Dictionary. There are eight VICAR2 parameters and four PDS parameters that specify the latitude and longitude boundaries of an image. LAT_UL and LAT_UR (both translate to MAXIMUM_LATITUDE in the PDS label) are the latitude of the center of the upper leftmost and rightmost pixel, respectively. LAT_LL and LAT_LR (both translate to MINIMUM_LATITUDE in the PDS label) are the latitude of the center of the lower leftmost and rightmost pixel, respectively. LON_UR and LON_LR (the larger of which translates to MAXIMUM_LONGITUDE in the PDS label) are the longitude of the center of the upper and lower rightmost pixel, respectively. LON_UL and LON_LL (the smaller of which translates to MINIMUM_LONGITUDE in the PDS label) are the longitude of the center of the upper and lower leftmost pixel, respectively. The keyword SUBF_COL (Y_AXIS_FRAMELET_OFFSET) is the column number of a framelet, which can have a value of 1 to 8. The keyword SUBF_ROW (X_AXIS_FRAMELET_OFFSET) is the row number of a framelet, which can have a value of 1 to 7. The MAP_RESOLUTION keyword in the PDS label is the value of SCALE given in the third equation above." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = 'DAVIESETAL1989' END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = 'SNYDER1987' END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = 'LYONS1988' END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG END_OBJECT = DS_MAP_PROJECT_INFO_CATALOG END_OBJECT = DATA_SET_MAP_PROJECT_CATALOG END